The purpose of this project, entitled "Chemistry Support Services for the National Toxicology Program's (NTP) Experimental Toxicology Branch (ETB)", is to provide chemistry support services to the National Toxicology Program (NTP), Experimental Toxicology Branch (ETP). The resources of the contractor will be used to: 1) provide special handling of the bulk chemicals such as purification or particle size reduction that may be needed prior to use in dose formulations; 2) identify low level impurities that may have an impact on the evaluation of the toxicology study results; 3) generate information for some test chemicals on stability in the proposed dose vehicle as well as the maximum concentration that can be achieved to assist in study design; 4) evaluate and resolve analytical problems encountered by the toxicology contractors and 5) provide chemistry support for in-house studies including routine preparation, analysis and delivery of dose formulations. The contract obtained under this project is not a continuation of a prior contract but rather represents the changed concept at NIEHS for acquiring chemistry support. Under the new concept, responsibility that heretofore had been split between an analytical support contractor and a toxicology contractor are consolidated under the toxicology contractor. This contract, for support for the Experimental Toxicology Branch, is consistent with the two recent chemistry support contracts; one supporting the Chemical Carcinogenesis Branch, N01-ES-15306 with Midwest Research Institute, and one supporting the Systems Toxicity Branch, N01-ES-15307 with Research Triangle Institute.